2001: A Space Odyssey on one level considers the birth, ascent and re-birth of mankind into a “star child”, gazing serenely upon the Earth and us, the viewer, with untold possibilities. Alien represents the Freudian nightmare tucked away in the recesses of the mind, a disturbing perversion of birth: life from death, invasive and toxic.

A little known influence for the chestburster scene was screenwriter Dan O’Bannon’s Crohn’s disease, a digistive disorder. According to Jason Zinoman’s book Shock Value: How A Few Eccentic Outsiders Gave us Nightmares, Conquered hollywood And Invented Modern horror, “The digestion process felt like something bubbling up inside of him, struggling to get out.” From this pain came the idea of the alien punching its way out of John Hurt’s chest during the Nostromo crews “last supper”.

After Kane (Hurt) has been attacked by the facehugger bursting forth from the disturbed egg on the “space jockey” craft, he is brought back aboard Nostromo. When it surprisingly detaches itself later and he awakes, seemingly unharmed, the crew retire to the mess for a last meal before returning to hypersleep for the trip home. On page 51 of O’Bannon and Ron Shusett’s script, the next cycle of the alien lifeform makes its shocking exit, and entrance:

“Kane’s face screws into a mask of agony. A red stain, a smear of blood, blossoms on his chest. The fabric of his shirt rips open and a small head, the size of a fist, punches out.”

Principal photography took place at Shepperton studios. When John Hurt began to react violently and thrash about, the other actors restrain him across the table. A clever edit from one side to the other allowed a gap for technicians to place Hurt beneath the table. Only his head and arms remained above, and a fake chest cavity lay across the table, from which the beast would burst forth. Amusingly, during the long set ups, Hurt would remain in that position, smoking a cigarette.

The other actors had of course read the script, but they had no idea how visceral the scene would be. The chest cavity was stuffed full of organs and pigs blood from the local meat factory. Under the hot studio lights the smell quickly became revolting. When the actors came on set, the crew were all wearing waterproof ponchos. Four cameras were ready to roll for optimum footage. Sigourney Weaver could see the screenwriters huddled in the corner, gleefully awaiting the mayhem to come.

A thin cut was made in the cavity T-shirt so that it would rip easily when the puppeteer below thrust the creature upwards. At first it didn’t come through, so when they tried again the actors were already leaning in, and the amount of blood that burst forth really shocked them. Veronica Cartwright got a face full and actually flipped right over in surprise on the now slippy floor. She realised the cameras were still rolling and had to scramble back in shot.

To have the creature then shoot off across the table, a slit was cut through it, and someone yanked the puppeteer, who was lying on a small camera dolley. The tail whipping back and forth was achieved by inserting a thin tube through it and pumping it with compressed air. It is telling that there are no outakes of actors or crew bursting into laughter. The atmosphere was highly charged; nothing like this had ever been seen before.

The film critic David Thomson can attest to the stories of audience members leaving when the scene came up, repulsed and disturbed: his wife left, he stayed, fascinated. John Hurt, a well known actor being snuffed out so brutally early in the film, was akin to Janet Leigh’s surprise dispatch in Psycho’s shower scene. But this was the 1970′s, and blood was spilled in eye-popping claret, not squeamish black and white.

In space, no-one can hear you scream. But across the world, at each fresh screening, audiences would be heard to scream, and scream again. Horror, specifically body horror, would never be the same.